The present invention relates to a semiconductor laser device.
Conventionally, there have been semiconductor laser devices to be incorporated in pickup units of information recording and reproducing apparatuses for personal computers as shown in FIG. 7. Such semiconductor laser device includes a stem 101 having a laser diode 102 and a light receiving element 103 mounted thereon, a protect cap 104 welded or bonded to the stem 101 for protecting the laser diode 102 and the light receiving element 103, and a holographic element 105 mounted on the protect cap 104. The protect cap 104 has a structure without an aperture for sealingly enclosing the laser diode 102 and the light receiving element 103 so that the laser diode 102 and the like is not affected by dust or foreign substances from the outside.
Recently, the pickup units have been commonly and widely applied to CD (Compact Disk) players for automobile use and to car navigation systems using CD-ROM (Compact Disk Read Only Memory) or DVD-ROM (Digital Versatile Disk Read Only Memory), as well as to the information recording and reproducing apparatuses for personal computers. The pickup units for use in vehicle are exposed to severer environment, especially in summer time when the temperature is raised, than the environment of the pickup units in use for personal computers installed inside of the room. The conventional semiconductor laser device has a laser diode 102 disposed inside the protect cap 104 without an aperture, which prevents radiation of heat from the laser diode especially under the severe environment. Eventually, the temperature of the semiconductor laser device is raised, which causes a problem that deterioration of luminous efficiency and change of emission wavelength may easily occur.